Hydraulically operated reciprocating mechanism



Oct. 1, 1-940. v 5,216,486

HYDRAULICALLY OPERATED REC IPROCATING MECHANISM Filed Sept. 6, 1938 3Sheets-Sheet 1 Oct. 1, 1940. 5 A CQQKE 2,216,486

HYDRAULICALLY OPERATED RECIPROGATING MECHANISM Filed Sept. 6, 193aSheets-Sheet 2 v wranfzr, a 5776/07/5- Oct. 1, 1940. E. A. COOKE2,216,486

HYDRAULICALLY OPERATED RECIPROCATING MECHANISM Filed Sept. 6, 1938 3Sheets-Sheet 3 Y 2 rr X4345 mama Oct. 1, 1946 UNITED STATESHYDRAULIOALLY OPERATED RECHROCAT- ING MECHANISM Ernest Albert Cooke,Leicester, England, assignor to Kapella Limited, Leicester, England, acompany of Great Britain Application September 6, 1938, S erial'No.228,719

In Great Britain September 17, 1937 12 Claims. (Cl. 121-45) 7 Thisinvention relates to hydraulically operated reciprocating mechanism andin particular to mechanism by which a vertical reciprocation is impartedto some movable element, for example, part of a machine tool,,having anappreciable weight.

The object of the invention is to provide a mechanism which will have asmooth reciprocatent of any pipe lines or circuits which are notincorporated in the apparatus to which the mechanism is applied andwhich will not be subject to air locks or other causes of disturbance.

For the sake of convenience the upper face of r a piston will bereferred to as an upper piston face while the under face of a pistonwill be referred to as an under' piston face.

According to the present invention the reciprocatingmechanism'comprises' two pistons'mounted on a common rod and operatingin separate cylinders, a supply of high pressure liquid being admittedfrom a high pressure circuit alternately L to one under piston face andone upper piston face of the same effective area to cause reciprocationof the pistons while a supply of low pressure liquid from an independentlow pressure circuit is admitted to the other under piston face as thepistons move upwards.

The two chambers to whichthe high pressure liquid is admittedalternately will be referred toas the working chambers.

The flow of liquid in the high, and in some cases also in the lowpressure circuit, is controlled by one or more valves, the arrangementbeing such that the high pressure liquid flowing to the 40 two-workingchambers does so without change of direction when the direction ofmovement of the pistons changes while the liquid in the low pressurecircuit always flows in the same direction.

Preferably the high pressure liquid is admitted alternately to the underface of the upper piston and the upper face of the lower piston whilethe independent supply of low pressure liquid is admitted to the underface of the lower piston as the pistons rise.

It will be seen that the low pressure liquid provides the necessaryresistance to overcome the effect of gravity upon the weight of thereciprocating elements and it will be understood that pressures in thehigh and low pressure circuits 56 and the rate at which the highpressure liquid and the low pressure'llquid is allowed to escape isdetermined in accordance with the speed of reciprocation desired, theweight of the reciproeating elements and other factors. I The main valveis conveniently of the piston 5- type and is reciprocated in a suitablecylinder adjacent to the working cylinders so asto control ports in thelatter, the movements of this valve being effected by apparatus underthe con-r trol of the working pistons. Thus this main valve 10 mayitself be hydraulically reciprocated by liquid pressure convenientlycontrolled by means of a pilot valve which is also preferably of thereciprocating piston type and is actuated by means of adjustable stopscarried by or connected to a part of the movable element to whichreciprocating movement is imparted by the working pistons.

The main valve may be provided with cushioning means to eliminate shockat the end of each stroke. f 20 In some cases the pilot valve may beomitted" and reciprocation of the main valve may be elfected by means ofsolenoids.- the circuits of which are alternately closed by means ofare-' versing switch actuated by the stops on the mem- 25 her to whichreciprocation is imparted. In such a case the main valve can besimplified, and instead of being arranged in a chamber adjacent to theworking cylinders, may be at any point convenient to the various pipelines through which 30 the high and low pressure liquid is circulated.Further, the high pressure liquid can be supplied to and exhausted fromthe lower cylinder through the same valve port'and the low pressureexhaust pipe may remain permanently open to the lower 35 working pistonscontrolled by a main valve and 50. 4 a pilot valve, the various circuitsbeing'diagrammatically shown,

Figure 2 is a vertical section on an enlargedscale -of an alternativeconstruction of working pistons provided with sleeve valves,

Figure 3 is a similar view of the lower working piston in its upperposition during the discharge of low pressure liquid, and

Figure 4 is an elevation, partly in vertical section, showing anelectrically operatedmain valve and a modified arrangement of high andlow pressure circuits.

The arrangement illustrated in Figure 1 comprises a common piston rod Icarrying a lower piston 2 and a similar upper piston 3, each operatingin separate coaxial chambers. The movements of these pistons aretransmitted to a ram 4 which, in eifect, constitutes an extension of theupper piston 3 and carries a jacket or casing 5 to the upper end ofwhich are secured adjustable stops 8 for controlling the pilot valve inthe manner hereafter described.

The space 1 below the under face of the upper piston 3 and the space 8above the upper face of the lower piston '2 constitute the high pressureworking chambers while the space 9 below the piston 2 constitutes thelow pressure chamber, to which low pressure liquid is admitted.

Mounted in a cylindrical bore, adjacent and parallel to the workingpistons, is a main valve x of the piston type which is reciprocated tocontrol the admission of high pressure liquid to and the escape of thisliquid from the two working chambers, and also to control the escapeoflow pressure liquid from the chamber 9, as. hereafter more fullydescribed.

The low pressure liquid which may be supplied froma tank A by means of apump H is at a much lower pressure than the high pressure liquid. Itexerts no appreciable force on the upwardly moving pistons and issupplied through a separate supply pipe I2 provided with a nonreturnadmission valve l3. When the piston 2 descends, the low pressure liquidescapes through an outlet port, hereafter described, controlled by themain valve X and so provides the necessary resistance to counteract theeffect of gravity on the reciprocating element 5 and any member it maysupport.

In the construction shown, the main valve X is hydraulicallyreciprocatedby means of a column of liquid alternately admitted through pipes II andI5 toopposite ends of the main valve chamber and this liquid column iscontrolled by means of a pilot valve l6 which is actuated by theadjustable stops 6 secured to the reciproeating element 5. The pilotvalve may be at any convenient point on the machine without specialreference to the position of the main valve.

The upper cylinder inlet port la is formed near the lower end of theupper cylinder, and the upper outlet port lb is above it andcommunicates at all times with an annular recess in the upper piston 3.Ports and passages 3a in the piston 3 establish communication betweenthe annular recess surrounding the piston and the upper workingchamber 1. At the upper end of the lower-working chamber 8 is a port 8athrough which high pressure liquid is admitted and exhausted, and theport 81) in the lower working chamber enables low pressure liquid tobeexhausted when it passes through passages 21; in the lower piston intothe annular space surrounding this piston.

The above ports lb, la, 80., 8b communicate with the chamber in whichthe main valve X reciprocates and are controlled by the main valve asfollows. The valve X comprises a hollow rod with closed ends carrying aseries of spaced pistons which divide the valve chamber into a series ofspaces X -X x being the uppermost and x being the lowest. Ports in thehollow valve rod establish communication between the interior of the rodand the spaces X X and X. The delivery side of the high pressure pump l1communicates through the pipe IS with the annular space X and highpressure liquid is also supplied to the spaces X and X The space X is atall times in communication with the upper outlet port 1b, and when thevalve moves upwards from the position shown in Figure 1, can also bebrought into communication with an upper relief port l9 communicatingwith the liquid tank A.(from which both high and low pressure pumps aresupplied) by means of a pipe 20 containing a throttle 20b. The space Xis in constant communication, through a lower relief passage 2|, withthe relief pipe 20 of the high pressure circuit and can be broughtinto-communication with the combined inlet and outlet port 8a of thelower working chamber 8.. The space X communicates with the low pressureoutlet pipe 22 only when the valve X is raised from the position shown,whereupon the low pressure fluid passes back to the tank A through thepipe 22.

The dimensions of the spaces and position of the various ports is suchthat when the valve X is in its lower position, as shown, the space Xcommunicates with the upper inlet port Ia allowing high pressure liquidto enter the upper working chamber 1 and the space X lies wholly belowthe upper relief port l9 which is closed, as it communicates only withthe annular space X while the outlet port 8b is similarly closed. Thespace X communicates with the combined inlet and outlet port to in thelower working chamber and with the lower end of the relief passage 2|.The working pistons 2 and 3 are therefore moved upwards by-the highpressure liquid admitted to the upper working chamber 1 and low pressureliquid is admitted through the non-return valve l3 without exerting anyappreciable force on the pistons.

When the valve X is in its upper position, the space X communicates withthe upper outlet port 1b and with the upper relief port l9 through whichhigh pressure liquid in the upper working chamber 1 can be dischargedthrough the port 30; the space X communicates with the upper inlet portla which is thus closed; "space X communicates with the combined inletand outlet port 8a through which high pressure liquid is thus deliveredto the lower working chamber 8, and the space X communicates with thelow pressure outlet port 8b and with the passage 22 leading back to thetank A through which the low pressure liquid in the chamber 3 can bedischarged. With the valve in this position, the working pistonsagain-descend at a rate determined by the throttling resistance in thepipes 20 and 22. This movement of the main valve'is controlled by thepilot valve which is reciprocated by engagement between the stops 6 anda head lGa formed on the rod of the pilot valve l6. High pressure fluidis supplied ,to the pilot valve through a pipe l8a and returns to thetank A by a pipe 23. When the pilot valve is in the position shown, highpressure fluid from the pilot valve chamber .is admitted into the upperend of the main valve chamber through the pipe l5; but when the pilotvalve is raised the port leading to the pipe I! is closed and liquid isadmitted to the main valve chamber through the'pipe ll. At each end ofits stroke the movements of the main valve are cushioned as some of theliquid is trapped between 7 malaise the plug at the end of the valve andthe recess into which these plugs enter. The flow of high pressureliquid and hence the speed of reciprocation is controlled by means ofthe throttlellb in the exhaust pipe 23, the low pressure-discharge pipe22 being also provided with a throttle, in-

dicated in dotted lines, which will 'not generally require adjustmentafter being initially set. The general arrangement described enables asupply tank to be used which is open to the atmosphere and hence air isnot trapped in the system and close control can be obtained even whencomparatively heavy elements are to be reciprocated.

The alternative construction illustrated in Figures 2 and 3 showsworking pistons provided with sleeve valves to control the ports in thepistons but intended for use with a similar main valve and with high andlow pressure circuits as already described. It will thus be' seen thatthe main valve Z is provided with pistons which divide it into nineannular chambers Z-Z, already described, high pressure liquid beingadmitted to the hollow bore of the main valve by a pipe Ila anddischarged through passages 2ld and 23a. Low pressure liquid'is admittedto the lower working piston through a non-return valve I34: and returnedthrough a pipe 22a.

A common connecting rod 24 is provided with a lower working piston 25and an upperWorking piston 26 to which is connected the ram 21 and amember similar to the casing shown in Figure 1. Instead of the annularspace surrounding each working piston communicating with the underpiston face bymeans of ports which are constantly open, as in theconstruction last de- 'scribed, each of the working pistons is providedwith a sleeve valve. The pistons are similar in this respect and thefollowing description is intended to read only on the iower-of these twosimilar pistons. The piston 25, as before, is provided with an annularrecess in which are formed a number of radial holes 28 communicatingwith an annular groove 29 formed in the bore of the piston. Mounted toslide in the piston bore is a sleeve 30 having at its lower end aninwardly projecting flange- 3| which is cut away so as to permit fluidto pass between the sleeve and the piston rod, and also provided with anumber of radial apertures 32. The interrupted flange 3| forms anabutment for a coiled spring 33 and the downward movement of the sleeveis limited by a suitable shoulder formed on the spacer 34 (for the upperpiston) or 35 (for the lower piston);

Grooves 34a and 35a are formed in the shoulders so that fluid is free topass into the bore of the piston even when the sleeve is in its lowestposition. As the opposite ends of each sleeve 30 are of differentefiective areas, very little extra force is required to compress thelight spring 33 in order to connect the apertures 32 with the holes 28in the piston, and thus to place the annular recess surrounding thepiston in communication with-the underside of the piston, as shown inFigure 3.

' These sleeve valves 30 are intended to permit the lower piston faceand the'top and bottom piston' rings to be used to the best advantageand to prevent piston creep. The construction provides-each piston witha self -contained low pressure valve so that the cut-off X and X can beeliminated and the. low pressure fluid can be evacuated from the lowercylinder without passing through the reversing valve. j

On the underface of the piston 23a small flange or projection 26aisshown so that there is an back to the liquid tank A annular clearancebelow the piston. Practically the whole area of this piston face istherefore exposedto pressure should the-piston assume the position shownin Figure 2.

In practice, springs of different strength will be 5 employed for theupper and lower pistons but for the purpose of this description the twoconstructions may be regarded as generally similar. The

, operation of the main valve and the wayin which it cooperates with theports in the working chaml0 hers is in accordance with the descriptionalready given with reference to Figure 1, but it will be seen thatinstead of the pressure liquid having constant access to the annularspace surrounding each working piston, by the provision of the sleevevalves, communication is only established with such annular spaces whenthe pressure liquid is being exhausted or discharged.

In the simplified construction illustrated in Figure 4, the upper andlower working pistons 36 and 31 are mounted on a common connecting rod38 and are provided with sleeve valves, as in the constructionillustrated in Figures 2 and 3. The

reciprocating jacket or casing 39, which is connected to the workingpistons, is provided with adjustable stops 40, but instead of thesestops actuating a pilot valve, as in the constructions alreadydescribed, they operate a spring-controlled reversing switch-4l by whichthe circuits of the solenoids 42 and 43 are alternately closed so as tobring about the reciprocation of a simplifled main valve. This valve Yis somewhat diagrammatically shown as mounted in a suitable "housingadjacent to the switch 4|, although, of

course, the valve can be in any suitable position. v

The valve comprises a hollowrod with closed ends, carrying a series ofspaced pistons which divide the valve chamber into five "spaces Y Y Y YY Ports in the hollow valve rod establish communication between theinterior of the 40 vinder is discharged through the pipe 46 into thevalve chamber and thence by the pipe 41 back to-the liquid tank A Athrottle 41a is provided in the pipe 41 by which the rate of flow of thehigh pressure liquid and hence thespeed of reciprocation can becontrolled.

Upward movement of the working pistons brings the stop 40 into contactwith the operating member of the pivoted reversing switch, so that thecircuit of the solenoid 43 is opened, the so solenoid 42 is energised,and the valve rod is thus moved towards the left. As a result, highpressure liquid is admitted into the upper end of the lower cylinderthrough the pipe 46, the low pressure liquid, owing to the operation ofthe g sleeve valve which the piston 36 contains, being returned throughthe pipe 22b to the tank A The high pressure liquid below the upperpiston 36 passes through the sleeve valve in that piston to the pipe 48and thence through the pipe 41 10 The reversing switch is then againswung over so that the cycle of operations is repeated.

It will be seen that in the construction last described the low pressurepump is eliminated and the low pressure circuit depends upon the head ofliquid in the tank.

The valve illustrated is provided at either end with a spring-loadedsleeve Y --Y adapted to limit the movementof the valve and to cushionits movement prior to being brought to rest, but

it is to be understood that the construction is.

given by way of example only and that the drawings are of a relativelydiagrammatic character.

It will further be appreciated that the invention is capable of a numberof applications and although the constructions above described areparticularly suitable for use with a machine tool such, for example, asan abrasive wheel, the invention is not limited to such use and many ofthe constructional details may be varied in accordancewith theparticular purpose to which the invention is put.

What I claim as my invention and desire to secure by Letters Patent is:

1. Hydraulically operated reciprocating mechanism comprising two workingcylinders, an operating piston in each cylinder, a common piston rodconnecting the two pistons, a high pressure liquid supply circuit, meansfor admitting and exhausting high pressure liquid alternately to oneunder face of the lower piston and one upper piston face area so as tocause reciprocation of the pistons, an independent low pressure liquidsupply circuit, and means for admitting low pressure liquid to the underpiston face as the working pistons move upwards, and means forrestricting the flow of low pressure liquid as it is exhausted duringthe downstroke of the pistons to counteract the effect of gravity on thepistons.

2. Hydraulically operated reciprocating mechanism comprising .twoworking cylinders, an operating piston in each cylinder, a common pistonrod connectingthe two pistons, a high pressure liquid supply circuit, amain valve adapted to control the supply and exhaust of high pressureliquid alternately to one under piston face and one upper piston face ofthe same effective area so as to cause reciprocation of the pistons, anindependent low pressure liquid supply circuit, and means for admittinglow pressure liquid to the under face of the lower piston as the workingpistons move upwards, and means for restricting the flow of low pressureliquid as it is exhausted during the downstroke of the pistons tocounteract the effect of gravity on the pistons. 3. Hydraulicallyoperated reciprocating mechanism comprising .two working cylinders, anoperating piston in each cylinder, 2, common piston rod connecting thetwo pistons, a high pressure liquid supply circuit, means for admittingand exhausting high pressure liquid alternately to one under piston faceand one upper piston face of the same effective area so as to causereciprocation of the pistons, an independent low pressure liquid supplycircuit, means for admitting low pressure liquid to the under face ofthe latter piston as the. working pistons move upwards, meansforrestrictin'g the flow of low'pressure liquid as it is exhaustedduringthe downstroke of the pistons in order to counteract the effect ofgravity on the pistons, and throttling means for restricting the passageof high pressure liquid as it is exhausted whereby the speed of reciprocation can be controlled. l

4. Hydraulically operated reciprocating mechanism comprising twosuperimposed working cylinders, an operating piston in each cylinder, acommon piston rod connecting the two pistons, a high pressure liquidsupply circuit, a main valve adapted to control the supply and exhaustof high pressure liquid alternately to the under face of the upperpistonand to the upper face of the lower piston, an independent low pressureliquid supply circuit, and means for admitting low pressure liquid tothe under face of the lower piston as the working pistons move upwards,and means for restricting the flow of low pressure liquid as it isexhausted during the downstroke of the pistons to counteract the effectof gravity on the pistons.

5. Hydraulically operated reciprocating mechanism comprising twosuperimposed working cylinders, an operating piston in each cylinder, acommon piston rod connecting the two pistons, a high pressure liquidsupply circuit, a main valve adapted to control the supply and exhaustof high pressure liquidalternately to the under face of the upper pistonand to the upper face of the lower piston, an independent low pressureliquid supply circuit and means for admitting low pressure liquid to theunder face of the lower piston as the working pistons move upwards andmeans for restricting the flow of low pressure liquid as it is exhaustedduring the downstroke of the pistons to counteract the effect of gravityon the pistons, the,;main valve being adapted also to control a port inthe lower cylinder through which low pressure liquid is discharged.

6. Hydraulically operated reciprocating mechanism comprising twosuperimposed working cylinders, an operating piston in each cylinder, atcommon piston rod connecting the two pistons, a high pressure liquidsupply circuit, a main valve of the piston type adapted to control thesupply and exhaust of high pressure liquid alternately to the under faceof the upper piston and to the upper face of the lower piston, anindependent low pressure liquid supply circuit, and means for admittinglow pressure liquid to the under face of the lower piston as the workingpistons move upwards, said main piston valve also controlling theexhaust port through which low pressure liquid is discharged from thelower cylinder, and

means for restricting the flow of low pressure liquid as it is exhaustedduring the downstroke of the pistons to counteract the effect of gravityon the pistons.

7. Hydraulically operated reciprocating mechanism comprising twosuperimposed cylinders, an operating piston in each cylinder, a commonpiston rod connecting the two pistons, a high pressure liquid supplycircuit, means for alternately admitting said high pressure liquid toone under piston face and one upper piston face of the same effectivearea, means by which the high pressure liquid is discharged in the samedirection from both cylinders when the direction of movement" of thepistons changes, means for supplying low pressure liquid from anindependent source to the under face of the lower piston as the pistonsmove upwards, means for exhausting, without change of direction, the lowpressure liquid as the pistons descend' and throttling means to restrictthe fiow of low pressure liquid as it is exhausted to counteract theeffect of gravity on the pistons.

8. Hydraulically operated reciprocating mechanism comprising two workingcylinders, an operating piston in each cylinder having a spaceconnecting the two pistons, a high pressure liquid supply circuit, amain valve adapted to cononeupper piston face, a low pressure liquidsupply admitted to the under face of the latter piston as the workingpistons move upwards, a sleeve valve in each working piston adapted topermit a flow of liquid between each under piston face and the spacesurroundingthe piston when the pressure on the under face of the pistonis greater than that in the space surrounding the piston, and means forrestricting the flow of low pressure liquid as it is exhausted duringthe downstroke of the piston to counteract the eifect of gravity on thepistons.

,9. Hydraulically operated reciprocating mechanism comprising twoworking cylinders, an operating piston in each cylinder having a spacesurrounding the piston, a common piston rod connecting the two pistons,a high pressure liquid supply circuit, a main valve adapted to controlthe supply and exhaust of high pressure liquid alternately to one underpiston face and to one upper piston face, a low pressure liquid supplyadmitted to the under face of the latter piston as the pistons moveupwards, a sleeve valve in each working piston adapted to permit a flowof liquid between each under piston face and the space surrounding thepiston, when the pressure on the under piston face is greater than thatin the space surrounding the piston, means for restricting the flow oflow pressure liquid as.it is exhausted during the downstroke oi thepiston to counteract the efiect of gravity on the pistons,

each. of said sleeve valves comprising a sleeve mounted to reciprocatein a bore formed in the working piston, one end of the sleeve being oflarger eflective area than the other end.

erating piston in each cylinder having a space surrounding the piston, acommon piston rod connecting the two pistons, a high pressure liquidsupply circuit, a main valve adapted to control the supply and exhaustof high pressure liquid alternately to one under piston face and to oneupper piston face, a low pressure liquid supply admitted to the underface of the latter piston as the pistons move upwards, a springcontrolled the sleeve being of larger effective area than its upper end.

' 11. Hydraulicaliy operated reciprocating mechanism as claimed in claimin which the main valve controls only the high pressure fluid circuitand a sleeve valve included in the lower working piston controls thedischarge of the low pressure liquid.

12. Hydraulically operated reciprocating mechdependently respectively bya non-return inlet valve and by a sleeve valve mounted in the lowerworking piston. 1 ERNEST ALBERT COOKEL.

